Apparatus for indicating a coordinate position on a chart



Patented June 17, 1952 UNITED PST *TES EN? ossi- APPARATUS FOR INDICATING- A COORDI- NATE POSITION ON A CHART John BasilCopping, London, England, assignor to The Decca-Record Company. Limited, London, England, .a :British company Application November-'19, 1948, Serial No. 60,915

' In Great Britain November 21, 1947 1,.Claim. 1

This invention -relates to apparatus-for indicating a co-ordinate position on a chart.

"The invention has a particularapplicationnto aircraftnavigation in which the position of Ithe aircraft is iound bymeans of simultaneous measurements representing position lines in the field patterns'of a radio navigational aid. 1 These measurementsmay be regarded as -co-ordinates what may be regarded as a co-ordinate system defined by the radio field. For-eXamplein=the radio navigation systems known as hyperbolic systems, the radio apparatus provides twoor more indications each representing one particular hyperbolic line of a set of lines. "Theposition of the aircraft is determined by reference to .a

"chart on which there has to I be found the .point of intersectionof lines corresponding to the particular hyperbolic position lines indicated byzthe radio apparatus. 1 A considerable time; for example half a minute or more, maybe required :if

the-position is to be marked by visual interpolation on a simple chart having sets of hyperbolic -co-ordinate lines marked thereon. During. this procedure, at least two-independent co-ordinate indications must be usedconcurrently and unless a navigatoris oarried,.:the pilot has. to :give undivided attentionto the'chart forthistime.

"This invention has as. its. principal objectto provide means for rapidly and: accuratelyf:con-

verting .co-ordinate .measurementsinto a position on a chart.

According to this invention, apparatusfonindicating a co-ordinate position on a ch-artrcpm- .prises a first member movable,-relative towthe chart in one of the co-ordinate -directions,-;a-sec- .ond member carried-by the first.-member-. and

movable relative thereto in the'second' co-ordinate direction and means for settingsa-idxmembers in accordance withtheir respective ordinates sothat the required co-ordinate. position is indicated by the position -relative-to the chart of-a selected point on the .secondzimember. With distorted chart by a rectilinear.v co ;-or dinate;system .having .either linear orhnon-linearscales.

. In. apparatus adapted to indicatea position :with respect to. a. chart havingarectiline'atcoordinate system, said first membeiumay comprise i a transversely. movableislide. barand said; second :member. is. movable along. said: slide; bar.

v2 A lead screw maybe provided forotraversin the slide bar.

"The'meansflforr moving .the secondymember along the slide bar may. comprise arotatable shaft having its axis in the direction of: traverse of the slide bar,- an. element which is keyedg to said shaft so as to be turned as the shaft: is

rotated andwhich is adapted to slide 'alongsaid shafts as the slide bar .is traversed so as toremain in the same position relativeto the;slide bar and means operated by the rotation ofisaid element for moving said ;second member salons said slide bar.

Said element. may comprisea .drumzcarrying a :cord,---wire or the like ffor..d'rawing said-second "member alongsaid slide .bar.

" The following. is a description of one :embQdi- --ment of: the invention, reference being-made 5150 the :accompanying drawings, in; which f Figure' 1 is; a planview of:the.apparatus, FiguretZis.a;seotion:a1ong the line; 2 ;2 of

--Figure l, and

Figure" 3 .is: a :blockdiagram showing, a;;ch a,rt position ::indicator of the character described,

arranged tosbeoperated directlylby a radio navi- "gational aid receiver.

' Insidethe casing :10; there is :provided a pair of: parallel bars; ll,: vI2 which-have their; ends secured in.two.: spacing members 13, M which extend along "the :sides of the casing. Slidably mounted onthe-two bars is a transversegmember l5 which bymeans ofsupports. l6, at'itsi'ends 1 carriesaslidell l -extending in a directionatright angles to. the direction of the bars. 'Ihe, transverse member I5 may be traversed alongatheybars x-H, l2 means ofa'lead screw [8 which-flies between. andparallel to the bars and whichuis carriedzat its ends'in bearings .irr'the spacing members. 'J'Keyedtothe lead screw near its ends are pinions 19,120 which meshwith the"v wheels i 2 I; 22 secured on. a shaft '23. which is paralleltxto the :lead screw and extends through bearingsin the spacing -membersl3, [4. Suitable knobs' -Z'l are fitted tothe end of the shaft 23 for manual operation. Also lyingbetween and parallel to the-bars l l2 is af-shaftil 25 having; askeyway extending: along its length. The eendsflof the shaft extend'ithrough ibearings in; .the. spacing -members I3', M. and are-also provided withknobs passessthrough two downwardly -extending-..por-

26 for manual operation. The shaft '25talso tions '21. of the transverse member'l 5 and aidrum 28 is located on the: shaft between thesexdownwardly extending portions. The-drum hasakey engaging-thekeywayon the.;shaft'25:so that it :canbe. rotated by means of the knobs :26. eWhen the transverse member is traversed along its bars by means of the lead screw 18, the downwardly extending portions 21 will cause the drum 28 to slide along the shaft 25.

The slide I! which is mounted on the transverse member preferably comprises two parallel strips of transparent material 29, 30 and is provided with two inwardly directed flanges 3|, 32 on which slides an indicating element 33 which is also made of transparent material. This element is moved along the slide I1 by a wire 34 wound around the aforementioned drum 28, the wire running over the two freely mounted drums 35, one at each end of the transverse member 15.

The chart 36 is mounted on an aluminium sheet which may be inserted between the trans verse member and the slide ll. One edge of this sheet is provided with two slots 31 which extend inwardly for a short distance and which are adapted to engage two locating pins 38 on the spacing member [4. These pins are threaded and provided with nuts for securing the chart. The chart 38 may be seen through the transparent indicating element 33 on which cross lines may be engraved. Preferably, however, the centre of the indicating element is provided with a hole 39 through which the point of a pencil may be inserted to mark the position of the indicating element on the chart.

The indicating element may be moved in one direction across the chart by rotating the lead screw [8 by means of the knobs 24 and at right angles to that direction by rotating the shaft by means of the knobs 26. The gear ratio of the pinions I9, 20- is so chosen that equal amounts of the knobs 24, 26 will cause substantially equal movements of the indicating element in the two directions. The shaft is arranged so that these directions coincide with the axes of rectilineal co-ordinates when the chart has been aligned by means of the locating pins 38. Thus the indicating element 33 may rapidly be brought to any required co-ordinate position on the chart by rotating the knobs 24 and 26 in accordance with their respective ordinates. To facilitate this adjustment, a pointer 40 is provided at one end of the slide I! which traverses a scale 41 along one side of the chart. A second scale 42 is provided along a side of the chart parallel to the transverse member and a pointer 43 may be traversed along this scale by means of a wire drive (not shown) operated by a fixed drum 44 secured to the shaft 25 so that the pointer 43 moves in synchronism with and indicates the position of the indicating element 33 along, its slide H. The pointer 43 is slidably mounted on a member 45 which extends between the bars II and I2 and lies above the chart 36. Suitable stops may be provided for preventing the indicating element moving along the slide l1 beyond the limits of the chart. These stops are preferably arranged on the drive and may take the form of a movable rack engaging a pinion on the shaft 25 and abutments to limit the travel of the rack.

Although the chart must be drawn to rectilineal co-ordinates, it will be appreciated that, if desired, it may be distorted by making the scales non-linear and constructing the chart to correspond to the non-linear scales. Such distortion does not affect the construction of the apparatus in any way but merely that on a particular chart the scales and the chart are distorted in a corresponding manner.

The whole assembly may be made portable or, if used in an aircraft, may be mounted in the pilots cockpit. A suitable pocket may be pro vided on the underside of the casing to accommo date the charts not in use. A sliding lid may be provided to cover the upper face of the apparatus and preferably provision is made so that the lid may be withdrawn completely and stowed on the underside of the casing when the apparatus is being used. The charts may be covered with a transparent film and different charts may be mounted on the two sides of the aluminium sheet. Appropriate lighting may be provided to illuminate the chart in use. When used in an aircraft to determine a position corresponding to two position line indications provided by a radio navigational aid, the chart is distorted so that two sets of position lines of the navigational aid become, on the chart, a. rectilineal co-ordinate system. The chart may be marked with a line indicating the route required to be followed by the aircraft and with lines indicating constant distances on either side of the route. Additional information may be provided, e. g., mileage along the route, bearings of courses, features of the terrain and danger zones. The chart may also be provided with markings near the knobs on the lead screw and shaft indicating the particular radio receiver responses to which the knobs correspond.

When the apparatus is used with a radio navigational aid, the lead screw l8 and the keyed shaft 25 may be driven automatically in accordance with the responses of a receiver which movesv in a radio field of such a character as produces in a pair of coordinate position indicators 5| and 52 driven by the receiver two changing responses from which a navigational fix may be obtained. For example the shafts 23 and 25 might be coupled to the indicating meters 5| and 52 through torque multiplying drives 53 and 54. The receiver 50 may comprise a part of the navigational aid such as is described in United States Patent No. 2,530,903 issued November 21, 1950 to William J. OBrien. In the aforementioned hyperbolic systems of radio navigation, it is usual to provide a receiver giving three responses of which only two are used at any one time. With such a system, the chart is constructed for two selected responses. If the drives 53 and 54 operate in accordance with changes in the responses, means such as slip clutches 55 and 56 are provided for permitting setting the indicating elements in their correct positions.

I claim In a chart position indicator for indicating a geographical location in terms of a nonrectilineal coordinate system, the combination of a chart of a geographical area embracin said location, said chart being so distorted that said non-rectilineal coordinate system is represented on said chart by two intersecting families of parallel straight lines; a housing including means for releasably holding said chart in an exposed position fixed relative to said housing; a pair of spaced parallel bars in said housing below said chart extending along opposite side edges thereof; a transverse member extending between said bars below said chart; means mounting said transverse member on said bars for sliding movement therealong; a lead screw threadedly engaging said transverse member mounted for rotation in said housing; a first manual control means on the outside of said housing connected to one end of said lead screw to permit said screw to be rotated manually; a transparent slide above said chart extending thereacross directly above and parallel to said 5 transverse member; connecting means at the ends of said transverse member beyond said side edges of said chart joining said slide to said transverse member; a transparent indicating member mounted on said slide for sliding movement therealong over the face of said chart; a transverse shaft extending through said housing parallel to said lead screw below said chart; a second manual control means on the outside of said housing secured to one end of said shaft to permit said shaft to be rotated manually; a drum; means mounting said drum on said shaft for rotation by said shaft and for sliding movement along said shaft; means on said transverse member engaging said drum for so sliding said drum as said transverse member is moved; a pair of idler rollers at opposite ends of said transverse member; and a wire wound around said drum, each of the end portions of said Wire passing around a different one of said idler rollers and back over the face of said chart, the ends of said Wire being secured to opposite sides of said indicating member, whereby rotation of said first manual control means moves said indicating member across the face of said chart in one direction, and where- 2 by rotation of said second manual control means moves said indicating member across the face of said chart at right angles to said one direction.

JOHN BASIL COPPING.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,370,645 Hawkes Mar. 8, 1921 1,408,504 Hammond et al Mar. 7, 1922 1,433,070 Conners Oct. 24, 1922 1,437,400 Conners Dec. 5, 1922 1,482,606 Goldrick Feb. 5, 1924 1,710,555 Tascarella Apr. 23, 1929 2,027,529 Hammond Jan. 14, 1936 2,058,306 Fowler Oct. 20, 1936 2,131,952 House Oct. 4, 1938 2,169,532 Jensen Aug. 15, 1939 2,198,757 Bohrn et a1 Apr. 30, 1940 2,342,938 Hopkins Feb. 29, 1944 2,422,025 Luck June 10, 1947 2,455,164 Ebeling Nov. '30, 1948 2,469,129 Reimann May 3, 1949 FOREIGN PATENTS Number Country Date 81,073 Sweden July 31, 1934 255,014 Italy Oct. 4, 1927 

